The color flip line of green/white to white/green on the leaf gives a very nice effect. It works especially well because the object has allot of detail. But this effect is way at the top so it really doesnt have much impact.
To have more effect I think the color flip line would have to come down a bit, but then you'll have all that white space at the top...heck I duno.
How about this.
Keep the leaf in the same possition. Instead of having the green space go margin to margin make it a green rectangle on a white background. That way you have white space all around with bits of green leafs sticking out on some or all sides...just a though.
[edit]Hmm i think that would look like a hary rectangle then...oh hell ignore me